Bright nickel electroplating bath containing sulfo-oxygen control agent nitrogen-containing brightener and minor concentration of terminal acetylenic alcohol or derivative

ABSTRACT

THIS INVENTION COMPRISES AN IMPROVEMENT IN A BRIGHT NICKEL PLATING BATH IN WHICH PREVIOUSLY TROUBLESOME PLATING AT CURRENT DESITIES OF LESS THAN 8 A.S.F. OR EVEN UNDER 15 A.S.F. IS AVOIDED BY USING A COMBINATION OF ADDITIVES COMPRISING (A) A SULFO-OXYGEN CONTROL AGENT, (B) A NITROGEN-CONTAINING BRIGHTENER, NAMELY AN AROMATIC MONOAMINE OR AROMATIC POLYAMINE, AN UNSUBSTITUTED POLYETHYLENEPOLYAMINE OR A NITRILE, AND (C) FROM 0.0005 TO 0.1 GRAM PER LITER OF AN ACETYLENIC ALCOHOL HAVING THE FORMULA HC$C-R IN WHICH R IS A HYDROXY-SUBSTITUTED HYDROCARBON RADICAL HAVING 1-8 CARBON ATOMS THEREIN SELECTED FROM THE CLASS CONSISTING OF HYDROXY-SUBSTITUTED ALKYL, ALKENYL AND CYCLOALKYL GROUPS AND THE ALKYLENE OXIDE ADDUCTS THEREOF CONTAINING NO MORE THAN 4 ALKYLENE OXIDE GROUPS AND THE ALKYLENE GROUP THEREIN HAVING 1-4 CARBON ATOMS.

5 Claims ABSTRACT OF THE DISCLOSURE This invention comprises an improvement in a bright nickel plating bath in which previously troublesome plating at current densities of less than 8 a.s.f. or even under a.s.f. is avoided by using a combination of additives comprising (a) a sulfo-oxygen control agent, (b) a nitrogen-containing brightener, namely an aromatic monoamine or aromatic polyamine, an unsubstituted polyethylenepolyamine or a nitrile, and (c) from 0.0005 to 0.1 gram per liter of an acetylenic alcohol having the formula HC= =CR in which R is a hydroxy-substituted hydrocarbon radical having 1-8 carbon atoms therein selected from the class consisting of hydroxy-substituted alkyl, alkenyl and cycloalkyl groups and the alkylene oxide adducts thereof containing no more than 4 alkylene oxide groups and the alkylene group therein having 14 carbon atoms.

This application is a continuation-in-part of Ser. No. 619,187, filed Feb. 28, 1967, now abandoned.

The present invention relates to improvements in the electrodeposition of nickel, relating more particularly to bright nickel plating baths utilizing certain addition agents to improve the brightness of deposits produced therefrom while minimizing unsatisfactory deposits in areas of the cathode subjected to low current density during the electrodeposition. More specifically, this invention relates to nickel plating baths having specific concentrations and combinations of components which improve plating in low current density areas which have previously been troublesome at current densities of less than 8 a.s.f. or even under 15 a.s.f.

Addition agents or brighteners useful in producing bright nickel deposits are generally divided into two classes depending on their principal function which in turn depends on their structure. These have been adequately described in the literature (F. Lowenheim, Modern Electroplating, 1963, John Wiley and Sons, Inc., N.Y.; A. H. Du Rose, Trans. IMF 38, 1961; and Metal Finishing Guidebook Directory, p. 288, 1965; U.S. Pat. 2,839,456 and U.S. Pat. 3,255,096).

Examples of the sulfo-oxygen control agents include the (a) mono and polynuclear aromatic sulfonic acids and salts thereof such as benzene sulfonate, 1,5-naphthalene disulfonate, p-diphenylether sulfonate, m-sulfobenzaldehyde and the like.

(b) aliphatic sulfonic acids such as allyl sulfonic, {3- styrene sulfonic, 2-bromoethane sulfonic, 3-iodopropane sulfonic and the like, either in the acid or salt form such as Na, K, Ni, etc.

(0) mono and polynuclear aromatic sulfonamides and sulfonimides, such as benzenesulfonamide, saccharin, p,poxy-bis (dibenzenesulfonamide), and the like (d) heterocyclic sulfonic acids such as thiophene sulfonic acid, 2-(4-pyridyl)ethyl sulfonic acid, and the like.

In general the sulfo-oxygen control agents or bright- United States Patent 0 ice eners of the first class are used in relatively high concentration and produce only semibright deposits. The brighteners or brighteners of the second class are used in low concentration and by themselves may or may not produce brightness or lustre.

When used conjointly, however, these two classes of addition agents produce fully bright deposits at least over certain current density ranges. Ordinarily the brightness of the deposit is satisfactory at the higher current densities of the order of 15 to 300 amperes per square foot (a.s.f.) because the brighteners function better at these current densities and because the deposit is thicker and has built-up brightness. Frequently, however, the deposit may not have satisfactory brightness at current densities less than 15 a.s.f. and especially at less than 8 a.s.f. This is a fault of the brightener system but may also be aggravated by impurities in the solution and lack of thickness. Although platings are generally conducted at much higher average current densities the recessed areas may be receiving a current density of less than 15 or even less than 8 a.s.f. Consequently the plating in such recessed areas very often does not receive a bright plating.

Sulfonate, sulfonimides or sulfonamides are used as the Class I brighteners or control agents. Sulfinic acids and sulfones are rarely used as the only Class I brightener. Numerous brighteners of this type are disclosed in the references cited above. The term sulfonic acid is generally used herein but the particular compound can be in the acid form or its salt form such as Na, K, Ni, etc., or mixtures thereof.

Of the Class II type brighteners those organic compounds containing nitrogen or the triple bond are predominantly used Aldehydes, ketones and labile sulfur compounds such as thiourea are rarely used in practice.

The compounds suitable as the nitrogen-containing (or- N-containing) agents of this invention are those having the nitrogen in the form of aromatic monoamines and aromatic polyamines, unsubstituted polyethylenepolyamines and nitriles. It is desirable that there be no groups in these compounds other than hydrocarbon, halogen, e.g. chlorine, bromine, etc., ether, thioe'ther, sulfonic, hydroxy, and carboxy. The hydrocarbon groups can be aliphatic, saturated or unsaturated, aromatic and cycloaliphatic. It is desirable that there be no mercapto groups (SH) present. Heterocyclic compounds containing more than one nitrogen atom per ring have not found favor as the principal brightener in nickel solutions and are undesirable as such for the purpose of this invention, as illustrated hereinafter.

Examples of the organic nitrogen compounds which have been used for this purpose are:

1) Nitrogen-containing triphenylmethane dyes, such as p,p',p-triamino-triphenylmethane, p,p'-diaminotri phenylmethane, Malachite Green, etc.

(2) p,p-Diaminodiphenylether, p-aminodiphenyl, etc.

(3) Unsubstituted polyethylene polyamines such as tetraethylenepentamine, polyamine-lOOO, etc.

(4) Nitriles selected from the group consisting of R'C- -N and AS (CH2) CEN, wherein R contains from 1 to 10 carbon atoms and is selected from the group consisting of alkyl, alkenyl, phenyl, benzyl and 2-phenylethyl, n is an integer from 1 to 4 and A is selected from the group consisting of:

m being an integer from 1 to 4.

(3) Alkyl (l to 4 carbon atoms) (4) Alkenyl (1 to 4 carbon atoms) (5) Alkynyl (1 to 4 carbon atoms) 2)n z)m Z n n n being an integer from 1 to 4.

It all c RN where R is independently H or alkyl, alkenyl or alkynyl of l to 4 carbon atoms.

The amines and cyano compounds are good brighteners and frequently are used in commercial bright nickel solutions. With a correctly formulated combination of these brighteners with control agents, bright deposits which have leveling properties can be produced. In many cases, however, if traces of metallic impurities such as Cu, Zn or Pb are present, the deposit in the low current density areas of the cathode is very often dark, dull or only semibright compared to the full brightness on the higher current density areas. Also, if the brightener concentration is too high the deposits in the low current density areas are very often dark, dull or only semibright compared to the higher current density areas.

Another type of Class II brighteners frequently used are the acetylenics or those containing the triple bond. In most cases these are acetylenic alcohols and may be loosely subdivided as follows.

Over-effective-These cause misplating and striating of the nickel deposit at low concentration and cannot under most conditions be used as brighteners because the harmful effects occur at a lower concentration than is needed for optimum brightness. These over-effective acetylenic alcohols are acetylenic alcohols having terminal triple bonds or their alkoxylated derivatives, Examples are propargyl alcohol, l-ethynyl-l-cyclohexanol and ethoxylated propargyl alcohol.

Moderately effective-These are non terminal triple bond alcohols, the most useful being Z-butyne 1,4-dio]. Used with the correct combination of control agents, this type, at relatively high concentration, will produce excellent bright deposits before the concentration is reached at which striation occurs. Although the brightness of the nickel deposit at the medium and high current density areas is excellent, that at a.s.f. or less is in most cases unsatisfactory. Ethoxylated butyne diol may also be used but the choice of control agents used with it is limited and to a certain extent it approaches the highly effective category with the accompanying disadvantages mentioned above.

IneffectiveThese are acetylenics which because of high molecular weight, insolubility and steric blocking of the triple bond are practically useless as brighteners. Even at the concentration where misplating and striating starts the deposit is still only semibright. An example is 3,6-dimethyl-4-octyne-3,6-diol.

It is well known to those skilled in the art that acetylenic brighteners have the tendency to cause misplating in the low current density areas (recessed areas) and even to cause striating of the deposit at normal or higher current densities. It is also known that certain labile sulfur compounds such as thiosulfate, sulfite, thiomalic acid, dithiomalic acid, mercaptobenzoic acid, and mercaptobenzimidazole will tend to eliminate darkness and misplating at low curernt density areas. They usually do this at the sacrifice of some brightness but under some conditions satisfactory deposits can be obtained although the low current density areas are not satisfactorily bright, having instead of a whitish appearance.

Also effective in eliminating or reducing misplating are the acetylenic or dienic carboxylic acid compounds of the copending application, Ser. No. 366,136, filed May 8, 1964, now abandoned. Here, the effect is surprising because some of these compounds themselves cause misplating when used alone.

Another class of compounds that reduce misplating caused by acetylenic brighteners are certain aldehydes and ketones, such as formaldehyde, bromal, acetonylacetonc, etc. These are quite useful in conjunction with acetylenics for producing semibright leveling deposits, but must be used judiciously in bright nickel because of their tendency to reduce brightness.

It has been found, and it is the subject of this invention, that an increase in brightness at low current density is produced when an over-effective acetylenic alcohol is added in controlled low amounts to a bright nickel solution which already contains a sulfo-oxygen control agent and a nitrogen-containing brightener. Two other surprising observations are noted:

(a) The addition of the highly effective acetylenic compound does not necessarily increase the brightness at the higher current density areas.

(b) The presence of the N-containing brightener decreases the harmful effect of the over effective acetylenic agent. The same concentration of over effective acetylenic agent would produce misplating or striations in the deposit if the N-containing brightener is not present. This effect is similar to that of the labile sulfur and aldehyde compounds previously described, the difference being that by this invention the low current density brightness is increased.

The over-effective acetylenic compounds useful in this invention are alcohols having the formula HCECR where R contains 1 to 8 carbon atoms and is a hydroxysubstituted alkyl, alkenyl, or cycloalkyl group, or an alkylene oxide adduct thereof having no more than 4 alkylene oxide groups. These are used in the low concentration of 0.003 to 0.1 g./l. The ethylene oxide adducts are especially advantageous because they have a lower volatility and can be used in a lower concentration than the parent alcohol. While an average of two ethylene or other alkylene groups seems to be optimum it has been found that a mixture of adducts containing one to four ethylene oxide groups has more effectiveness over a wider range. The reason for this is not known. It has also been observed that aged or air sparged products have a wider latitude in concentration range.

While any of the previously mentioned control agents or mixtures thereof may be used, the optimum results for the conditions of this invention are obtained when the larger proportion of the control agent is an aromatic sulfonamide or sulfonimide. The total sulfo-oxygen control agent concentration may vary from 0.2 to 20 g./l. but preferably is maintained at 24 g./l.

The concentration range for the N-containing brighteners is about 0.0005 to l g./l. depending on the type of compound.

The nitrogen-containing brighteners are those or similar to those which have been used before and include:

Aromatic amino compounds such as those described in US. Pats. No. 2,238,861 and No. 2,294,311, an example being p,p'-diaminodiphenylether. The preferred concentration is 0.0010.0l5 g./l.

Polyamines such as described in US. Pat. 2,662,853, an example being tetraethylenepentamine. The preferred concentration is 0.00050.1 g./l.

Nitriles, such as those described in the US. Pats. No. 2,524,010 and No. 2,978,391, examples being ethylene cyanohydrin. The preferred concentration is 0.00051.0 g./l. Also disclosed is the thioether, thiodipropionitrile, which is used in similar concentration.

These N-containing brighteners when used in their optimum concentration in conjunction with Class I brighteners produce fully bright deposits which are in most cases commercially satisfactory. However, they lack the ability to produce fully bright deposits at current densities below 8 or 10 a.s.f. and sometimes even below 15 a.s.f. The addition of a very low concentration of an over effective acetylenic brightener as defined herein while not necessarily enhancing the high current density brightness will increase the low current density brightness. If this same concentration of over effective alcoholic acetylenic agent is used without the N-containing brightener, very poor brightness is obtained or the deposit tends to be misplated or striated.

In the following examples cathode panels with a V bend are used such that the current density at the center bottom of the bend is about 3 a.s.f. and that at the higher current density area is about 45-80 a.s.f. These are plated in a Watts type nickel solution at a pH of 3.5-4.2 and temperature of 135-1 40" F. with mild air agitation. In the description a wide, large or broad semibright recess means that deposit is not fully bright at a current density of 3-15 a.s.f. A moderate sized recess refers to 3-8 a.s.f., and a narrow or small recess refers to 3-5 a.s.f. A distinction is sometimes made between semibrigh and bright semibright. The examples are given in consecutive steps which give the additions made. For example, b in each case has the components indicated for or added in a, and c also has the components of a and b. The results are as follows:

EXAMPLE I (a) 2 g./l. of naphthalene disulfonate+1 g./l. of saccharin. Deposit uniform semibright.

(b) 0.01 g./l. tetraethylene pentamine. Deposit bright with large dull dark-colored recess.

0.05 g./l. propargyl alcohol. Deposit bright with small bright semibright recess.

EXAMPLE II (a) Same as Ia. (b) 0.05 g./l. propargyl alcohol. Deposit badly striated and misplated in the recess.

EXAMPLE III EXAMPLE IV (a) Same as 11 1a.

(b) 0.0015 g./l. thiodipropionitrile. Deposit bright with moderate sized bright semibright recess.

(0) 0.016 g./l. diethyleneglycolmonopropargyl ether. Deposit bright with very narrow semibright recess.

EXAMPLE V (a) Same as IIIa.

(b) 0.03 g./1. diethyleneglycolmonopropargyl ether. Deposit not fully bright, is striated and is misplated in the recess.

EXAMPLE VI (a) Same as IIIa. (b) 0.004 g./l. thiodipropionitrile. Similar to IVb except the recess is larger and duller.

EXAMPLE VII (a) 2 g./l. p,p-oxy bis-( dibenzenesulfonarnide) plus 1 g./l. saccharin. Uniform semibright deposit.

(b) 0.008 g./l. p,p'-diaminodiphenylether. bright with large semibright recess.-

(c) 0.015 g./l. diethyleneglycolmonopropargyl ether. Similar to (b) but the semibright recess is much smaller.

EXAMPLE VHI The following acetylenic alcohols with terminal ethynyl groups are each used with 3 g./1. of p,p-oxy-bis-(dibenzenesulfonamide) and 0.0015 g./l. of thiodipropionitrile.

Deposit Each one increases the brightness in the low current density recess with the optimum at the concentration shown. Only a, b and e have the effect of also increasing the brightness of the high current density deposits:

6/]. (a) 3-butyne-2-ol .05 (b) 3-butyne-l-ol .07 (c) 4-pentyne-2-ol .03 (d) 2-methyl-3-butyne-2-ol .02 (e) 3-methyl-1-pentyne-3-ol .02 (f) 5-hexane-4-0l .04 (g) 3,5-dimethyl-1-hexyne-3-ol .04 (h) 1-ethynyl-l-cyclohexanol .04 (i) 7-oxtyne-5-ethyl-6-ol .06

Notice that there seems to be little relation between the molecular weight and the concentration needed to effect the improvement in the recess.

A particularly effective composition of this invention is a nickel plating bath containing:

(a) 1-10 g./l. of p,p'-.oxy-bis(dibenzenesulfonarmide);

(b) 00005-0008 g./l. of B,B'-thiodipropionitrile; and

(c) 0005-0015 g./l. of diethyleneglycolmonopropargyl ether.

A preferred specific composition 'of this type is one containing approximately 4 g./l. of component (a), 0.0015 g./l. of component (b) and 0.01 g./l. of component (c).

It should also be noted that the alkylene oxide adducts of the alcohols have an enhanced activity over the correspondi-ng alcohol, e.g. a lower concentration can be used for HC5CCHOC H OC H4OH than for HCECCHZOH This is illustrated by the amount of alcohol used in Example I as compared to the amounts of ethylene oxide adducts used in Examples III, IV and VIII.

Particularly preferred for this purpose are the adducts of the formula HCECCH (0C H 0H where n is 1 to 4.

For the purpose of this invention, other alkylene oxide adducts and chloro or hydroxy-substituted alkylene oxide adducts, such as prepared from propylene oxide, epichlorohydrin, butylene oxide, dioxolane, glycidol, etc. are considered as equivalents of the ethylene oxide adducts. These adducts can be mixtures of alkylene oxide adducts in which there are 1-4 alkylene oxide groups and also there can be mixtures of ethylene oxide, propylene oxide groups, etc.

The following examples demonstrate that acetylenic alcohols not having a terminal triple bond are inefifecitve for improving the low current density brighteners:

EXAMPLE IX (a) Same as IIIa.

(b) 0.01 g./l. p,p'-diaminodiphenylether. Deposit is bright with moderate sized bright semibright recess.

(c) 2-butyne-1,4-diol added in concentration from 0.1 to 0.5 g./l. There is no improvement in the low current density brightness and in fact at the higher concentrations of the diol, the semibright area increased.

Other types of addition agents may be added to effect certain benefits but frequently at the expense of other attributes of the deposits. For instance, small concentrations of coumarin or butyne diol may increase the leveling of the deposit at the higher current densities but they have the detrimental effect of decreasing the brightness in the low current density areas. Aldehydes such as bromal or formaldehyde may be used in certain cases to lower the sulfur content of the deposit. They may also be used in some cases to eliminate misplating when too much of the overly effective acetylenic alcohol or glycol has been used. These aldehydes likewise must be used judiciously since they tend to cause general dullness of the deposit if too much is used.

The nickel solutions of this invention like others can be operated at extremely high current densities if the agitation and/or temperature is increased. At 145 F. and an agitation rate equivalent to two feet per second, a current density of 300-400 a.s.f. may be used. They may also be operated at high current densities with insoluble anodes such as lead, in which case no chloride is used in the solution. At a temperature of 170 F. and a solution flow rate of 13 feet per second, bright deposits have been produced at over 1000 a.s.f. Under these conditions, the insoluble anodes oxidize some of the addition agents but the concentration of the addition agents needed at these high agitation rates is considerably reduced.

As stated previously the effective N-containing brighteners suitable for the practice of this invention are used at their optimum concentration, which optimum is the same with or without the over effective acetylenic compounds. These effective N-containing brighteners have been described above.

As in other bright nickel solutions metallic impurities such as copper or zinc may be harmful in that they cause dullness in the low current density areas. The presence of saccharin will intensify this harmful elfect.

We claim:

1. A composition adapted for bright nickel electroplating of a metallic base comprising an acidic aqueous solution of a nickel salt in which there is also dissolved effective amounts of:

(a) from 0.2 to 20 g./l. of an organic sulfo-oxygen control agent,

(b) from 0.0005 to 1 g./l. of a nitrogen containing organic brightening agent composed of a nitrile selected from the group consisting of R'CEN and A-S(CH -CEN; wherein R contains from 1 to 10 carbon atoms and is selected from the group consisting of alkyl, alkenyl, phenyl, benzyl and 2- phenylethyl n is an integer from 1 to 4 and A is selected from the group consisting of:

171 being an integer from 1 to 4 (3) Alkyl (1 to 4 carbon atoms) (4) Alkenyl (lto 4 carbon atoms) (5 Alkynyl (1 to 4 carbon atoms) 2)n 2)m 2 n n n being an integer from 1 to 4 where R is independently H or alkyl, alkenyl or alkynyl of 1 to 4 carbon atoms; (0) an acetylenic compound having the formula wherein R is an hydroxy-substituted hydrocarbon radical having 1-8 carbon atoms selected from the class consisting of hydroxy-substituted alkyl, alkenyl and cycloalkyl groups, and alkylenoxy derivatives thereof, the alkylene group of said alkylenoxy derivatives having 1-4 carbon atoms therein, said derivatives having no more than 4 alkylenoxy groups therein, and said acetylenic alcohol being present in a concentration of 0.0030.1 gram per liter of solution.

2. A composition adapted for bright nickel electroplating of a metallic base comprising an acidic aqueous solution of a nickel salt in which there is also dissolved effective amounts of:

(a) 1 to 10 g./l. of an organic sulfo-oxygen control agent;

(b) a nitrogen containing brightening agent com rising 0.00050.0008 g./l. of 6,5'-thiodipropionitrife; and

(c) an acetylenic compound comprising 0.003-0015 g./l. of diethyleneglycol-monopropargyl ether.

3. The composition of claim 2 wherein the sulfo-oxygen control agent consists of p,poxy-bis(dibenzenesulfonamide).

4. The composition of claim 3 wherein the organic sulfooxygen control agent is used in an amount of 4 g./l.; the nitrogen containing organic brightening agent is used in an amount of 0.0015 g./l. and the acetylenic compound is used in an amount of 0.01 g./l.

5. A composition adapted for bright nickel electroplating of a metallic base comprising an acidic aqueous solution of a nickel salt in which there is also dissolved effective amounts of:

(a) an organic sulfo-oxygen control agent;

(b) a nitrogen containing organic brightening agent consisting of thiodipropionitrile; and

(c) an acetylenic compound having the formula HCECR wherein R is an hydroxy-substituted hydrocarbon radical having 1-8 carbon atoms selected from the class consisting of hydroxy-substituted alkyl, alkenyl and cycloalkyl groups, and alkylenoxy derivatives thereof, the alkylene group of said alkylenoxy derivatives having 1-4 carbon atoms, therein, said derivatives having no more than 4 alkylenoxy groups therein, and said acetylenic alcohol being present in a concentration of 0003-01 gram per liter of solution.

References Cited UNITED STATES PATENTS GERALD L, KAPLAN, Primary Examiner 

